The present disclosure relates to an image forming apparatus that allows an intermediate transfer unit to be inserted into and pulled from an apparatus main body.
An image forming apparatus including an intermediate transfer unit having an endless transfer belt extended on and between a plurality of rollers is widely known. In the image forming apparatus, the intermediate transfer unit can be inserted into and pulled from an apparatus main body in a horizontal direction. In addition, rail members for guiding horizontal movement of the intermediate transfer unit when the intermediate transfer unit is inserted or pulled are provided in the apparatus main body. That is, each rail member is provided with a guide groove extending from an end portion thereof at the upstream side in an inserting direction toward the downstream side in the inserting direction, and the guide groove guides the intermediate transfer unit while supporting a rotation shaft of the roller, when the intermediate transfer unit is inserted or pulled. Moreover, a positioning groove is provided at a deep portion of the guide groove at the downstream side in the inserting direction so as to be engageable with the rotation shaft, and the rotation shaft is brought into engagement with the positioning groove, thereby restricting movement of the intermediate transfer unit in the inserting/pulling direction. Furthermore, an arm member is provided which presses the rotation shaft engaged with the positioning groove, in a direction in which the rotation shaft is caused to fit into the positioning groove. The arm member restricts displacement of the roller and further displacement of the intermediate transfer unit.
Meanwhile, in such a type of an image forming apparatus, in an image non-forming period when an image forming operation is not performed, the intermediate transfer unit is driven by a predetermined drive mechanism such that all photosensitive drums and primary transfer rollers do not nip the transfer belt therebetween. At this time, the rotation shaft is displaced against a biasing force of the arm member in a direction in which the rotation shaft escapes from the positioning groove.